Such joining plants for manufacturing body shells are known from practice. They comprise a cyclically operating conveyor for the workpieces, which is designed, e.g., as a lifting shuttle. The joining plant is divided here into a plurality of stations, which are arranged along the conveyor or transfer line and in which different joining tasks are performed by robots on the stationary workpiece, the robots being arranged stationarily in the stations on one or more sides of the transfer line. This design has the drawback that a relatively large number of robots is necessary, and the robots as well as the tools are not utilized optimally. Due to the binding to stations and working on the stationary workpiece, there is a fixed binding to the cycle time, and, in addition, the robots have a limited working range only. The overall cycle of the joining plant also includes, besides the working time, the conveying time as an appreciable component, which adversely affects the efficiency. Furthermore, there is an increased distance between the robots at the transitions from one station to another due to the binding to stations, which increases the space requirement. Since the robots machine only partial areas on the stationary workpiece, a plurality of robots and also a plurality of tools of the same type must be used for tasks of the same kind on the front and rear sides of the workpiece.
Assembly on moving bodies is known from DE 195 20 582 C1. The assembly robot is moving in this case along an additional travel axis in the conveying direction, synchronously with the body, and is coupled with the body conveyor for this purpose. After the end of the assembly job, the robot must be returned into its starting position. This leads to increased space requirement in the conveying direction. Moreover, it is not possible to line up a plurality of robots at closely spaced locations next to one another in the conveying direction.
DE 35 16 284 A1 likewise pertains to the performance of assembly operations on a moving vehicle body. Assembly robots with an additional linear axis, which move synchronously together with the vehicle being conveyed and must be returned after the completion of the job, are present here as well.
DE 199 31 676 C2 teaches the measurement of a body, which is stationarily resting during the measuring operation. The measuring robot has an additional linear axis, with which it can change its basic working position. It must be zeroed again at the new measurement site on the basis of stationary calibration marks.
DE 101 36 691 A1 pertains to the compensation of position errors of a robot by means of a laser measuring instrument. This is only a calibration operation. In addition, a welding tool and a workpiece can also be measured and calibrated with the measuring instrument, which simplifies and expedites the calibration operation.
DE 24 30 058 A1 discloses a position measuring system for robot members and is used to measure and calibrate a robot with compensation of its axis error.